The overall objectives of the proposed research are: a) to obtain an understanding of the hormonal regulation of spermatogenesis; b) to clarify the role of the Sertoli cells in spermatogenesis; c) to utilize biochemical techniques to obtain information on the biological maturation of the seminiferous tubules; and d) to further develop cell culture techniques to effect these aims. Specific objectives of this proposal are: a) to characterize primary cultures of Sertoli cells from rats and mice of all ages; b) to investigate the effect of testosterone and other steroids on FSH stimulated DNA synthesis in the Sertoli cell culture; c) to isolate and analyze the secretory proteins of Sertoli cells and to determine the hormonal influences on secretory protein synthesis; d) to determine the effect of FSH on DNA polymerase and thymidine kinase activity; e) to investigate the effects of FSH or testosterone on spermatogonial division, differentiation or degeneration in cell culture; f) to determine if the influence on DNA synthesis in spermatogonia is mediated through the Sertoli cells; g) to obtain and characterize continuous cell lines of Sertoli cells obtained by transformation and to utilize these cell lines for a genetic and molecular examination of Sertoli cell function.